class Solution {
    public int removeDuplicates(int[] nums) {
    
        if (nums == null) {
            return 0;
        }

        int i = 0;
        for (int j=1; j<nums.length; j++) {
            if (nums[i] != nums[j]) {
                i++;
                nums[i] = nums[j];
            }
        }

        return i+1;

    }
}